1. Field of the Invention
The invention relates to a hybrid vehicle and a method of controlling a hybrid vehicle.
2. Description of the Related Art
Heretofore, there have been known hybrid vehicles equipped with an engine and a motor as power sources and running with one or both of them being suitably selected. One of such hybrid vehicles (disclosed in JP-A-2002-122061) is constructed as follows. This hybrid vehicle is provided with a heat accumulator that maintains part of engine coolant at a certain temperature. When a starter switch is closed, the hybrid vehicle waits in a state where running by a motor is possible. If coolant in the heat accumulator is higher in temperature than coolant in the engine by a predetermined degree or more, the coolant in the heat accumulator is delivered into the engine. After the temperature of the coolant in the engine has reached a predetermined preheating temperature, the engine is started.
In this hybrid vehicle, however, the preheating of the engine is started when the starter switch is switched from OFF to ON. Therefore, the preheating of the engine is started, for example, even when a driver turns the starter switch ON simply for the purpose of listening to music on an onboard stereo with no intention of starting to drive the vehicle. In such a case, heat accumulated in the heat accumulator may be wastefully consumed. On the other hand, since the engine is started after the temperature of coolant in the engine has reached the predetermined preheating temperature, an improvement in startability or exhaust emission properties is achieved in comparison with a case where the engine is started at a low engine temperature. However, there are demands for a further improvement in startability or exhaust emission properties.